feat: add Haskell Stack support (#546)

Add a Haskell Stack module when a stack.yaml file is detected

src/configs/mod.rs

@@ -11,6 +11,7 @@ pub mod git_commit;
 pub mod git_state;
 pub mod git_status;
 pub mod go;
+pub mod haskell;
 pub mod hg_branch;
 pub mod hostname;
 pub mod java;